Abstract

Na[V^IVO(O₃P(CH₂)₂CO₂)]·2H₂O, MIL-26, was synthesized hydrothermally at 453 K for 24 h under autogenous pressure. Its three-dimensional open structure was determined by single crystal X-ray diffraction. MIL-26 is monoclinic (space group P2₁, no. 4) with cell parameters at 293 K: a = 6.4041(3), b = 17.6252(8), c = 7.7271(3) Å, β = 95.586(2)°, Z = 4, V = 868.04(7) Å³. Its framework is constituted of double chains based on isolated V^IVO₆ octahedra linked by PO₃C tetrahedral groups of the [O₃PCH₂CH₂CO₂]³⁻ organic cations. At the other end of each organic chain, CO₂⁻ chelates a VO₆ octahedron of a neighbouring chain. Each double chain is connected to four others by these organic chains thus defining elliptical channels along [100] in which water molecules and Na⁺ cations are located.